Revert "Refactor walkDirTree to use fs.FS"

This reverts commit 3853c3318f.

utils/paths.go

@@ -0,0 +1,18 @@
+package utils
+
+import (
+	"os"
+
+	"github.com/navidrome/navidrome/log"
+)
+
+func IsDirReadable(path string) (bool, error) {
+	dir, err := os.Open(path)
+	if err != nil {
+		return false, err
+	}
+	if err := dir.Close(); err != nil {
+		log.Error("Error closing directory", "path", path, err)
+	}
+	return true, nil
+}